BRUSSELS -- This week's conviction in Estonia of former senior defense official Herman Simm as a Russian spy ends what officials have described as the biggest espionage scandal in NATO's history.

The question weighing most heavily on the minds of intelligence professionals in Estonia, at NATO, and allied capitals is the extent of the real damage done by Simm. The costs will not only be counted in systems compromised or plans leaked, but also in terms of loss of reputation, credibility, and prestige.

Simm's career as a Russian spy spanned a staggering 12 years. After Estonia joined NATO in 2004, Simm was until 2006 a "gold-card operative," to quote one Estonian security official. As head of Estonia's National Security Authority, he had full access to many NATO secrets and an intimate knowledge of its procedures.

Estonian Prosecutor-General Norman Aas told journalists in Tallinn on February 25 that investigators have established that Simm managed to pass on large amounts of material to his Russian handlers.

Aas said that "between the summer of 1995 and his arrest last September," Simm gave Russia's Foreign Intelligence Service (SVR) at least "a few hundred" classified Estonian and NATO documents.

Estonian officials have indicated the documents misappropriated by Simm include information about the deployment and battle plans of the Estonian armed forces on what is possibly NATO's most vulnerable flank.

Alliance Networks Compromised

Officials at NATO headquarters in Brussels declined to comment for this article, saying the alliance never discusses intelligence matters publicly. "NATO takes this very seriously," one NATO spokesperson said, however.

Correspondingly, the damage caused by Simm to NATO remains a matter for speculation. Western European media reported last fall that teams of intelligence officials from NATO headquarters converged on Tallinn after his arrest. Their findings have not been made public.

Simm's heyday fell in the period 2004-06, after which he was moved to a different post. Simm, now 61, retired in early 2008. Given these dates, it is unlikely that Simm could have seriously compromised NATO's cyberdefense project, spearheaded by Estonia in the wake of a wave of attacks on the country's Internet network in 2007.

Missile-defense issues and the war in Georgia would have also fallen largely outside the period of Simm's unfettered access to NATO secrets

What is more likely is that Simm compromised the German-manufactured Elcrodat system, which manages phone, fax, and other communications traffic between Brussels and NATO member states, as reported by the German weekly "Der Spiegel" on November 17, 2008.

This is an impression borne out by comments made by the director of the Estonian Security Police, Raivo Aeg, to Estonian television on February 26. "There was no irreversible catastrophe," Aeg said. "However, the information Herman Simm passed on partially compromised and caused damage to various data systems, communications systems, and the like."

Aeg said Simm's spying resulted in "fragmentary" damage that will not necessitate the reconstruction of any systems from scratch.

The French weekly "Le Nouvel Observateur," quoting unnamed sources, reported that Simm's responsibilities included the supervision of Estonia's bilateral military cooperation with other countries. Thus, he would have been privy to all information relating to arms deals, been able to visit classified locations, and been familiar with intelligence personnel.

There has been no official reaction to Simm's arrest or conviction from Russia, Aeg said.

New Members At Arm's Length

Unlike Aldrich Ames, the Russian spy within the CIA, unmasked in the United States in 1994, Simm is said by officials to have cost neither Estonia nor its allies any "blown" agents -- or their lives.

In purely intelligence terms, the damage caused by Simm is also likely to have been limited by most allies' reluctance to share hard-won information with any but a very few trusted allies. The United States, Britain, France, and Germany -- to name the countries with the largest intelligence operations -- carefully filter the data they make available to NATO with its 26 members.

But the Simm case is likely to reinforce suspicions by some of NATO's core countries that the new members can't be fully trusted.

Alastair Cameron, head of the European Security Program at the London-based Royal United Services Institute, says that even before the Simm affair, corruption in the new member states, as well as their immature political and judicial systems, were seen as risks.

Estonian authorities say Simm was paid at least $100,000 for his services to the Russian secret service, but possibly a lot more. The fact that Simm's opulent lifestyle, frequent holidays, a portfolio of a half-dozen well-heeled properties, and his collection of expensive paintings did not cause Estonian authorities to start asking questions earlier will have been noted in other NATO capitals.

Simm's Russian contact was identified by Estonian authorities this week as Sergei Yakovlev, alias Portuguese entrepreneur Antonio de Jesus Amorett Graf, resident in Madrid, and Simm's handler since 2002. "Le Nouvel Observateur" said its sources suggest Yakovlev has been arrested and is waiting to be exchanged for a Western agent in Russia.

And what of Simm himself? He is reported to have claimed that he was recruited by the KGB as a young law enforcement officer already before the fall of the Soviet Union. After independence, he remained a "sleeper" until 1995, when contact with him was resumed by the KGB's successor in foreign espionage, the SVR. Simm claims the SVR started blackmailing him, while Estonian authorities tend to emphasize Simm's need for recognition and reward as someone who had risen to the rank of colonel in the Soviet Union only to lose that status in Estonia after 1991.

The authorities also released a brief video recording of an interrogation, where a resigned-looking Simm says, "What is done, is done, and will have to be paid for." His 12 1/2-year sentence -- less than the 15-year maximum for treason -- was said to have been the result of a plea bargain. This removed the need for a potentially lengthy, damaging, and embarrassing appeals process.

The plea bargain may also have allowed his wife, Heete Simm, walk free. Estonian authorities admit they believe she was complicit in Simm's treason, but say they do not have enough evidence to prosecute her. Simm was also ordered to pay the Defense Ministry 20 million Estonian kroons (about $1.6 million) in damages.

The fact that someone like Simm could spy for Russia for personal gain has come as a shock in Estonia, which has always prided itself on having made possibly the cleanest break with its communist past among the former Soviet republics and satellites.

But while Estonia's civil service brims with young faces, there has never been a complete break with the Soviet past. The country's current prime minister, Andrus Ansip, was a high-ranking communist functionary in Soviet Estonia, Interior Minister Jueri Pihl is a product of the same Soviet-era law enforcement system as Simm, and Estonia's EU commissioner, Siim Kallas, was part of the Soviet Estonian nomenklatura in the 1980s.